Imaging in psoriatic arthritis: established methods and emerging techniques.

Psoriatic arthritis (PsA) is a heterogeneous, chronic, inflammatory musculoskeletal disease that can lead to peripheral and axial damage and loss of function. A clear difference between PsA and other forms of inflammatory arthritis is the different forms of bone remodeling seen in PSA which incorporates not only increased bone resorption with bone erosions, osteolysis, and loss of bone mineral density but also increased bone formation with periostitis, syndesmophytes, enthesiophytes, and ankylosis. PsA, if diagnosed late, will lead to significant structural damage, the most severe form of which is known as arthritis mutilans, and loss of physical function. Imaging plays a crucial role in diagnosing and monitoring both peripheral and axial conditions associated with PsA. Radiography is currently the main modality used to monitor structural damage in PsA though commonly used scoring systems do not include bony proliferation as a criterion. Besides, radiography is limited in determining the presence and cause of periarticular soft tissue thickening, which may arise from tendinosis, tenosynovitis, synovial proliferation, bursitis, or enthesitis. Recently, much more attention has been paid to determining the imaging characteristics of PsA, which enables more precise identification of disease and severity assessment. Newer imaging technologies also enable variations in normal bone microstructure to be distinguished from disease-related abnormality. This review discusses the current state of innovative imaging modalities in PsA, specifically concentrating on their roles in PsA diagnosis and treatment, improving the early detection of PsA, and identifying patients with skin psoriasis at risk of developing psoriatic arthritis.